A new paper finds that for forest biodiversity to recover, conservation management should be informed by monitoring all threats to vertebrates, including those below the canopy. 

Research published today in The Proceedings of the Royal Society B: Biological Sciences identifies exploitation as a key driver of the decline in the population of species that depend entirely on forests (‘forest specialists’) and recommends a new global indicator for use in wider forest biodiversity recovery efforts.

This comes following the publication of The State of the World’s Forests 2020, which found that tackling global biodiversity loss is utterly dependent on conserving the world’s forests. Forests harbour most of the Earth’s terrestrial biodiversity, including 80 percent of amphibian species, 75 percent of bird species, and 68 percent of mammal species.

However, this research found that forest vertebrate populations have halved between 1970 and 2014. Biodiversity loss is a critical environmental challenge with grave implications for human wellbeing and valuable ecosystem services, from providing food and clean water to carbon storage.

In order to better understand the drivers of this loss, the authors developed a new global indicator - the Forest Specialist Index – to analyse trends in forest specialist vertebrate populations.

They also analysed the relationship between change in tree cover and the populations of forest-dwelling vertebrates worldwide, and revealed that forest area is a poor indicator of forest biodiversity status. Investigating the known threats to the same species identified exploitation as a key driver of forest specialist population decline.

As a result, focusing on forest area alone risks masking other pressures on forest vertebrates that can exist below the canopy. For example, while further research is needed, evidence suggests that the negative trend in mammals could be the result of targeted hunting, particularly in the tropics.

This emphasises the importance of complementing satellite-derived datasets with repeated on the ground species surveys and site-specific threat information when assessing the status, trends and drivers of forest biodiversity change. This could help to reduce the risk that so-called empty forests - forests that have lost many of their large mammals - go undetected.

These findings have policy implications for the post-2020 Global Biodiversity Framework currently under development. While the Conference of the Parties to the Convention on Biological Diversity is delayed, work continues to draw up a new deal for nature with associated targets for the next decade, including strengthened monitoring and accountability measures.  This paper highlights the role that the Forest Specialist Index could play alongside existing indicators to give a fuller picture of forest biodiversity.

Will Simonson, Senior Programme Officer, Climate Change and Biodiversity, UN Environment Programme World Conservation Monitoring Centre (UNEP-WCMC), says:

“Conserving forest biodiversity is key to tackling the global nature crisis. In order to understand and prevent forest biodiversity loss, we cannot rely on monitoring forest area alone. It is crucial to look below the canopy and identify site-specific threats to species to safeguard our forests into the future.”

‘Below the canopy: global trends in forest vertebrate populations and their drivers’ was written by experts from UNEP-WCMC, the Institute of Zoology, Zoological Society of London, and WWF-UK.